In a conventional foldable mobile terminal such as a foldable portable telephone device, a notebook computer, or the like, a key input part is provided in a first housing, a display part formed of a liquid crystal display device is provided in a second housing, and the second housing is supported with respect to the first housing through a hinge and the like so as to be freely opened/closed. The foldable mobile terminal is used in a state in which the housings are opened at the time of key input, and it can be carried in a state in which the housings are closed when not in use.
FIG. 10 is an external view showing a conventional foldable portable telephone device 700 in a state in which second housing 702 is open. In the conventional foldable portable telephone device 700, first housing 701 and second housing 702 are connected to each other through hinge portion 703 to be supported so that they can freely be opened/closed. First housing 701 includes ten keys 704 for inputting telephone numbers and soft keys 705 in the same plane. Furthermore, first housing 701 has side face key 707 having a plurality of functions, that is, by pushing for a long time, turning on/off power supply, inputting start or end of phone conversation, and further switching displays.
Herein, soft keys 705, which are controlled by a control part (not shown) mounted in the first housing, disposed immediately below soft key icons 710 displayed on display part 708 of the second housing so that soft key icons 710 and soft keys 705 are in one-to-one correspondence. By pushing soft key 705 located nearest to soft key icon 710, a function specified by the soft key icon is allowed to operate.
FIG. 11 is an external view showing the above-mentioned conventional foldable portable telephone device 700 in a state in which second housing 702 is closed. Second display part 711 is provided at the outside of second housing 702 and can display the time, received telephone number, or the like, even in a state in which second housing 702 is closed. Furthermore, by pushing side face key 707 with second housing 702 closed, contents to be displayed on the second display part 711 can be switched. Note here that specific examples of a conventional notebook computer or PDA are not shown but they have substantially the same configuration as mentioned above.
The basic way of using these conventional foldable mobile terminals has been to perform key input in a state in which second housing 702 is open. The use of the conventional foldable mobile terminals in a closed state was limited to watching the displayed time, and the like. Therefore, in a state in which second housing 702 is closed, more highly complicated key input, for example, input for allowing certain functions of the foldable mobile terminal to operate, may not be able to be carried out.
Furthermore, Japanese Patent Unexamined Publication No. 2003-110675 discloses an example of a portable telephone with a slidable lid having a configuration capable of operating soft keys with a lid closed. This portable telephone with a sidable lid is provided with a display part and soft keys on the outer surface of the lid and the lid is allowed to slide on a main body having ten keys. In order to apply this structure to a foldable mobile terminal as shown in FIG. 10 in which second housing 702 is opened/closed by rotating it at a hinge portion, soft keys are added to the outer surface of the second housing 702.